Rubberized belting and method of making the same



Nov. 19, 1940. H. McKAY 2,221,984

-RUBBER IZED BELTING AND METHOD OF MAKING THE SAME Filed April 1, 1958 2Sheets-Sheet 1 lnvemoi" larva/m1- d Nov. 19-, 1940. H, MCKA 2,221,984

RUBBERIZED BELTING AND METHOD OF MAKING THE SAME Filed April 1, 1938 2Sheets-Sheet 2 inventor a Zi y Patented Nov. 19, 1940 UNITED ST TESPATENT OFFICE RUBBERIZED BELTING AND METHOD OF MAKING THE SAME HunterMcKay, Belmont, Mass, assignor to Boston' Woven Hose dz Rubber Company,Cambridge, Masa, a corporation of Massachusetts Application April 1,1938, Serial No. 199,405

. 8 Claims.

This invention relates to rubberized belting of the type whichincludesdnits structure alternate layers or plies of rubber and textilefabric vulcanized or cured under pressure.

*" The invention consists in belting of this type characterized by anovel surface configuration,

, the surface of belting, particularly leather belting, in order to giveits tract-ion surface a vacuum cup efiect, but such embossing has beensuperficial and has not modified the internal structure of the belting.My invention, on the con- 0 nary, contemplates a molding of thebeltingin which the underlying textile ply or plies have their threadsdisplaced by pressure transversely to the plane of the fabric so thatthey tend to approach an upright position in the surface lay- 5 er ofthe belting, extending as loops in the projecting portions, and beingdepressed below the depressions formed in the rubber surface layer.

In some cases the molding step may uncover the" fabric threads in thebottom of all or some of the depressions in the surface layer of rubber,and in other cases the molding step may be less severe, but it isdesirable, in accordance with my invention, to displace the threads tosome degree from the normal flat plane of the fabric so that in wear theupstanding threads will be expbsed in points separated from each otherby a vulcanized rubber filler.

The design of the surface is of secondary importance. It may be aregular geometric design or it may be irregular, for example, a designproduced by a coarse sand paper-matrix.

The invention includes within its scope the novel process hereindisclosed as a preferred manner of producing the novel belting of myinvention.

The nature of the invention will be best understood and appreciated froma consideration of the accompanying drawings illustrating a preferredembodiment of the belting and one step in the process of itsmanufacture. In the drawmgs,

Fig. '1 is a diagrammatic view in section illustrating the step ofmolding or embossing one surface of the belting, f

Fig. 2 is a fragmentary plan view of the belting, a portion being shownin magnified scale,

Fig. 3 is an enlarged view in side elevation of a portion of a belt outalong the line 3-8 of Fig. 2,

Fig. 4 is a diagrammatic view in section illustrating the step ofmolding both surfaces of the belting,

Fig. 5 is a view in side elevation on an enlarged scale showing theeffect of the molding at operation and illustrating a splice, and

Fig. 6 is a plan .view of Fig. 5, part being cut away. As indicated inFig. 3 the particular type of belting selected for illustrationcomprises four 145 plies I0 of woven textile material embedded in andspaced by five layers ll of rubber composition. In manufacturing suchbelting the rubberized fabric layers are coated with uncured rubber andare then assembled and subjected to w pressure and heat so that they arevulcanized into a solid integral mass. A commercial proces of makingbelting of this general type is disclosed in U. S. Letters Patent No.2,093,904 granted September 21, 1937, on an application of John 25 M.Bierer. The said patent also discloses apparatus for carrying out theprocess of manufacture and I contemplate employing the same apparatus inthe production of the novehbelting of my invention, although it is in nosense limfed about the periphery of the heated cylinder 20v under severepressure of the steel band 22. In its progress about the cylinder theribs 2| embed themselves completely in the material of the belt,

.- displacing the rubber of the surface layer and also the underlyingtextile ply in the configuration shown in Figs. 2 and 3, that is to say,the entire surface of the belting is criss-crossed with ribs l2 disposedat right angles to each other and defining pyramidal depressions in thebot tom of each of which is exposed or substantially exposed one or morethreads of the uppermost textile layer II in the body of the belting. Int addition to this visible evidence of displacement the moldingoperation causes a portion of the threads of the textile layer to bedisplaced upwardly into the tapering ribs of the surface configuration.In other words the individual threads are flattened in the valleys andtheir curvature intensified in the rib portions of the belting,imparting somewhat of a pile effect to the fabric. Thus in a single stepprocess the belting material is not only cured and vulcanized but hasimparted to it a surface configuration of the character described and astructural modification resulting in improvement of the traction andwearing quality of the product.

As shown in Figs. 4 and 5, I also contemplate molding both the upper andlower surfaces of the belting, and this may be accomplished by placing aflexible mold 24 on the surface of the pressure band 22, whereby thebelting 25 is molded on both surfaces. The mold 24 may be constructed ofany suitable flexible material. The result of such treatment isillustrated in Fig. 5 wherein the upper and lower textile plies 26 and21 are sharply peaked at various points and the center plies 28 areconsiderably flatter and more gently curved. The splice is indicated bythe staggered breaks at 2 9 in the textile plies and shown to be in aline oblique to the face of the belting. Belting molded on both surfacesis useful for driving many types of machines such as spindle machines.Furthermore, the double molding operation serves the additionaladvantage of clamping down the splice from both surfaces.

It will be understood that the outstanding advantage presented bybelting of the character above described is that its surface has ahigher coefficient of friction between the belting and the pulley orbetween the pulley lagging and belting than has been availableheretofore in commercial conditions, and this advantage continues as thebelting wears down in use. Therefore, the belting of my invention allowsthe transmission of more power or the carrying of greater load with lessslippage and lower initial or total tension in the installation thanheretofore. Besides increasing the efliciency of the belting, thisfactor tends also to increase its useful life since both slipping andhigh tension are detrimental in this respect.

In addition to the greater coeflicient of friction, the roughenedsurface when applied to endless belts is of material benefit in holdingdown the lip of the splice. The conventional belt is made endless byjoining staggered ends of the plies of two or more pieces of rubberizedfabric and vulcanizing the body of the belting. The splice is normallythe weakest part of an endless belt, there being a great tendency forthe extreme end or lip of the splice to curl up. The molding orembossing above described tends to clamp or bind down the splice so thatit is less likely to curl or open so readily. I desire it to beunderstood that my invention includes in its scope a belt having moldedpyramidal depressions limited to that portion of the belt which containsthe splice.

' Another advantage of the belting of my invention is in respect toappearance. The conventional smooth friction surface belting,particularly that made with light colored rubber compounds, revealsclearly the nature of the fabric weave as well as any imperfections ordefects therein. On the other hand, the roughened surface conceals thesecharacteristics and allows the production of belting within commerciallimits of any desired appearance regardless of the. character of thefabric used in its structure, and the fabric weave does not becomeapparent as the working surface or surfaces wear down.

The life of the belting is also increased because the embossing ormolding action tends to to increase or retain the natural crimp of thetextile fabric. In the case of woven fabrics this is true of both thewarp and filler. In rubberized belting as heretofore constructed thereis a tendency to spread the belting widthwise in the vulcanizing pressand this spreading reduces the already light initial crimp in thefabric. The rough molded or embossed surface tends to retard thisspreading and therefore increases the crimp especially in the filler.

In rubberized belts as heretofore constructed with smooth surface, thetextile fibres of the fabric lie more or less parallel wtih the surfaceof the belting. With normal wear and slippage these belts tend to becomeslick and shiny on the'surface with a serious resulting loss intraction. The molded or embossed belting on'the other hand, tends topeak certain portions of the fibres so that after some wear a pile-likesurface is produced. The treatment also tends to prolong thehighcoefllcient of friction in the belting. It will be noted also thatthe embossed or molded cavities serve for retaining belt dressing shouldsuch dressing be used.

Having thus disclosed my invention and described a preferred manner ofpracticing it, I

layers of rubber and textile fabric including a surface layer of rubberwith indentations and projections therein, the threads of the uppermostfabric layer being deflected downwardly beneath the indentations andupwardly into the projections of the'belting.

3. Rubberizedbeltingcoinprisingsuperposedlayers of rubber and wovenfabric including a surface layer of vulcanized rubber having a series ofindentations therein, each .of which substantially exposes a thread ofthe fabric in its bottom and contains an upwardly looped thread in itsside walls.

4. The process of making rubberized belting of superposed layers'ofrubber and woven fabric, which is characterized by the step of moldingindentations in a rubberized surface layer-of the belting andsimultaneously uncovering spaced threads of the underlying fabric torender them visible through the overlying rubber layer.

5. Rubberized belting comprising alternate layers of rubber and textilefabric including upper and lower surface layers of rubber withindentations molded therein of sufllcient depth to cause displacement ofthe fabric threads transversely of the surfaces of the belting.

6. The process of making rubberized belting of superposed layers ofrubber and fabric, which is characterized by the step of moldingindentations in the upper and lower rubberized surface layers of thebelting and simultaneously uncovering spaced threads of the underlyingfabric in the bottom of the respective indentations. I

7. The process of improving the traction and wearing qualities ofrubberized belting composed of layers of rubber and fabric, which ischaracterized by simultaneously vulcanizing the belting, causing thethreads of the outermost fabric layers to be peaked toward the workingsurface by depressing the fabric at spaced locations and causingdisplacement of the outer rubberlayer substantially uncovering shortlengths of the 1 0" thread of the underlying fabric layer.

8. The process of making rubberized belting of superposed layers ofrubber and fabric. which is characterized by simultaneously carrying outthe steps of vulcanizing the belting, molding indentations in itsworking surface, depressing and un-. I covering the thread of the fabricat the bottom of the respective indentations and causing the threadbetween said indentations to be displaced transversely with respect tothe plane of the fabric.

HUNTER. McKAY.

